W32/Mytob-GZ

Please follow the instructions for removing worms.

Replace the Hosts file from a backup or edit it in Notepad to remove the changes that the worm has made.

You will also need to edit the following registry entries, if they are present. Please read the warning about editing the registry.

At the taskbar, click Start|Run. Type 'Regedit' and press Return. The registry editor opens.

Before you edit the registry, you should make a backup. On the 'Registry' menu, click 'Export Registry File'. In the 'Export range' panel, click 'All', then save your registry as Backup.

Locate the HKEY_LOCAL_MACHINE entries:

HKLM\Software\Microsoft\Windows\CurrentVersion\Run

HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices

and remove any reference to any file you deleted.

Each user has a registry area named HKEY_USERS\[code number indicating user]\. For each user locate the entry:

HKU\[code number]\Software\Microsoft\Windows\
CurrentVersion\Run\

and remove any reference to any file you deleted.

Close the registry editor.

W32/Mytob-GZ is a mass-mailing worm and backdoor Trojan that can be controlled through the Internet Relay Chat (IRC) network.

Sophos's anti-virus products include Genotype ™ detection technology, which can proactively protect against new threats without requiring an update. Sophos customers have been protected against W32/Mytob-GZ (detected as W32/Mytob-Fam) since version 3.92. W32/Mytob-GZ is a mass-mailing worm and backdoor Trojan that can be controlled through the Internet Relay Chat (IRC) network.

When first run W32/Mytob-GZ copies itself to the Windows system folder as taskmr.exe and creates the following registry entries:

HKCU\System\CurrentControlSet\Control\Lsa
Windows Update
"taskmr.exe"

HKCU\Software\Microsoft\OLE
Windows Update
"taskmr.exe"

HKCU\Software\Microsoft\Windows\CurrentVersion\Run
Windows Update
"taskmr.exe"

HKLM\SYSTEM\CurrentControlSet\Control\Lsa
Windows Update
"taskmr.exe"

HKLM\SOFTWARE\Microsoft\Ole
Windows Update
"taskmr.exe"

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Windows Update
"taskmr.exe"

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
Windows Update
"taskmr.exe"

W32/Mytob-GZ copies itself to the root folder as:

eminem vs 2pac.scr
photo album.scr
funny pic.scr

and drops a file called sexymsn.exe (detected by Sophos as W32/Mytob-H) in the same location. This component attempts to spread the worm by sending the aforementioned SCR files through Windows Messenger to all online contacts. W32/Mytob-GZ also drops a file named nethell.exe which is detected by Sophos as Troj/Furoot-B.

W32/Mytob-GZ also appends the following to the HOSTS file to deny access to security related websites:

127.0.0.1 www.symantec.com
127.0.0.1 securityresponse.symantec.com
127.0.0.1 symantec.com
127.0.0.1 www.sophos.com
127.0.0.1 sophos.com
127.0.0.1 www.mcafee.com
127.0.0.1 mcafee.com
127.0.0.1 liveupdate.symantecliveupdate.com
127.0.0.1 www.viruslist.com
127.0.0.1 viruslist.com
127.0.0.1 viruslist.com
127.0.0.1 f-secure.com
127.0.0.1 www.f-secure.com
127.0.0.1 kaspersky.com
127.0.0.1 www.avp.com
127.0.0.1 www.kaspersky.com
127.0.0.1 avp.com
127.0.0.1 www.networkassociates.com
127.0.0.1 networkassociates.com
127.0.0.1 www.ca.com
127.0.0.1 ca.com
127.0.0.1 mast.mcafee.com
127.0.0.1 my-etrust.com
127.0.0.1 www.my-etrust.com
127.0.0.1 download.mcafee.com
127.0.0.1 dispatch.mcafee.com
127.0.0.1 secure.nai.com
127.0.0.1 nai.com
127.0.0.1 www.nai.com
127.0.0.1 update.symantec.com
127.0.0.1 updates.symantec.com
127.0.0.1 us.mcafee.com
127.0.0.1 liveupdate.symantec.com
127.0.0.1 customer.symantec.com
127.0.0.1 rads.mcafee.com
127.0.0.1 trendmicro.com
127.0.0.1 www.microsoft.com
127.0.0.1 www.trendmicro.com

W32/Mytob-GZ is capable of spreading through email and through various operating system vulnerabilities such as LSASS (MS04-011). Email sent by W32/Mytob-GZ has the following properties:

Subject line:

Mail Delivery System
Mail Transaction Failed
read it immediately
Server Report
Status
thanks!

Message text:

'This is a multi-part message in MIME format.'

'Mail transaction failed. Partial message is available.'

'The message contains Unicode characters and has been sent as a binary attachment.'

'The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.'

'The original message was included as an attachment.'

'I have received your document. The corrected document is attached.'

The attached file consists of a base name followed by the extentions PIF, SCR, EXE or ZIP. The worm may optionally create double extensions where the first extension is DOC, TXT or HTM and the final extension is PIF, SCR, EXE or ZIP.

W32/Mytob-GZ harvests email addresses from files on the infected computer and from the Windows address book. The worm avoids sending email to addresses that contain the following:

.gov
.mil
accoun
acketst
admin
anyone
arin.
avp
berkeley
borlan
bsd
bsd
bugs
ca
certific
contact
example
feste
fido
foo.
fsf.
gnu
gold-certs
google
google
gov.
help
iana
ibm.com
icrosof
icrosoft
ietf
info
inpris
isc.o
isi.e
kernel
linux
linux
listserv
math
me
mit.e
mozilla
mydomai
no
nobody
nodomai
noone
not
nothing
ntivi
page
panda
pgp
postmaster
privacy
rating
rfc-ed
ripe.
root
ruslis
samples
secur
sendmail
service
site
soft
somebody
someone
sopho
submit
support
syma
tanford.e
the.bat
unix
unix
usenet
utgers.ed
webmaster
you
your

Sophos's anti-virus products include Genotype ™ detection technology, which can proactively protect against new threats without requiring an update. Sophos customers have been protected against W32/Mytob-GZ (detected as W32/Mytob-Fam) since version 3.92.